I theorize that there exists a shadowy arm of the law that observes them, sort of like the old Stasi or KGB. When they have failed to observe a youngster smoking for a period of time, they take her off the street and stick her in a reeducation camp, where the kid is subjected to primitive but effective techniques of behavior modification.
She'll come out puffing, like her peers.
In a way, socialist societies depend on their smokers. Not just for confiscatory tax revenues from smokers when they are still earning, but also for their early demise from various cancers or heart disease, which eases the old-age pension burden on the welfare system.
[ One half of a ≤}B^) ]
But, you know, those Euros, they are so much more sophisticated than us redneck Americans. We could learn a thing or two from them. Like smoking, walking around with flasks of gut rot liquor to drink through out the day and stopping to urinate on the sides of roads in random places. All favorite Euro pastimes.